This invention relates to synthetic triglycerides containing C.sub.6-24 fatty acid residues, with the proviso that at least one residue is a conjugated linoleic acid residue, and to a process for the production of the triglycerides. The invention also relates to the use of the triglycerides in foods and pharmaceutical products.
Polyunsaturated .omega.-3 and .omega.-6 fatty acids, such as .alpha.-linolenic acid and linoleic acid, are among the fatty acids essential to mammals and human beings. Besides linoleic acid, other isomeric octadecadienoic acids occur in nature. They are distinguished by conjugated double bonds at carbon atoms 9 and 11, 10 and 12 and 11 and 13. These isomeric octadecadienoic acids are collectively referred to in the scientific literature as conjugated linoleic acids (abbreviation: CLAs) and have recently attracted increasing attention (NUTRITION, Vol. 19, No. 6, 1995).
Conjugated linoleic acids are present as constituents in various foods. Their main source are animal foods although significant quantities of CLA are also present in milk and milk products. In addition, CLAs have been found in various oils and fats, the concentration in vegetable oils being significantly lower than the concentration in animal fats (J. Food Compos. Anal. 5, 185-197 (1992)).
Various working groups have reported on the significance of CLAs to the organism. Recently, Shultz et al. reported on the inhibiting effect on the in-vitro growth of human cancer cells (Carcinogenesis 8, 1881-1887 (1987) and Cancer Lett. 63, 125-133 (1992)).
In in vitro tests, CLAs were tested for their effectiveness against the growth of malignant human melanomas, colon and breast cancer cells. In the culture media, there was a significant reduction in the growth of the cancer cells treated with CLAs by comparison with control cultures. The mechanism by which CLAs exert anticarcinogenic activity is unknown. In addition, CLAs have a strong antioxidative effect so that, for example, the peroxidation of lipids can be inhibited (Atherosclerosis 108, 19-25 (1994)).
Investigations have also been conducted, for example, into the addition of conjugated linoleic acid to foods for the purpose of color stabilization (JP 06/276939 A2).
The use of conjugated linoleic acid in animal feeds and, in this connection, also in human nutrition is known, for example, from WO 96/06605. This application is concerned with reducing body fat content in animal nutrition. In the statement of problem, the specification also mentions the possibility of application to human beings. In particular, it mentions the use of a fatty emulsion containing 0.5 to 2% by weight of conjugated linoleic acid for oral or intravenous administration to human beings.
EP 0 579 901 B relates to the use of conjugated linoleic acid for avoiding loss of weight or for reducing increases in weight or anorexia caused by immunostimulation in human beings or animals.
WO 94/16690 is concerned with improving the efficiency of food utilization in animals by administering an effective quantity of conjugated linoleic acid.
In connection with the many positive effects of conjugated linoleic acid, as demonstrated in intensive studies, particularly on animals and tissue cultures, the use of conjugated linoleic acid in foods for human consumption has also been discussed. However, the use of free conjugated linoleic acid in foods and pharmaceutical products is limited by the fact that, on the one hand, unwanted reactions with other food constituents can occur where free conjugated linoleic acid is incorporated in complex foods and, on the other hand, by the unpleasant taste and odor of conjugated linoleic acid which can lead to non-acceptance by the consumer. Another disadvantage is that free fatty acids are covered by food additive legislation so that their use in foods is restricted.
Accordingly, the complex problem addressed by the present invention was to find a substitute for conjugated linoleic acid, above all in human nutrition and also for pharmacological use. On the one hand, this substitute would have better organoleptic properties than conjugated linoleic acid and, on the other hand, would lend itself to incorporation in foods without initiating secondary reactions.